If you want more distance and consistency, use a proper weight shift. Imagine a pole coming vertically out of the ground where the ball is resting at address. Make it your goal to get your left shoulder behind the ball and the imaginary pole on the takeaway--without swaying the hips. This ensures a good position to initiate your downswing. On the follow-through, your right shoulder should move past the ball and imaginary pole. When you do this correctly, you not only make a good turn, but a good weight shift as well.
The real secret to hitting straighter, more-consistent shots is to have a square clubface at impact. If your clubface connects squarely with the ball, your shots fly straight. It's that simple! One way to promote a square clubface at impact is to have one at the top of the backswing. If you're not square at the top, you have to manipulate the club in some way to make it square at impact. This can lead to all kinds of timing problems. Here's a good drill that teaches you how to play from a square position. With a club in hand, lift your arms just up to the forehead, and then rotate the shoulders as far as possible, allowing a full backswing. This sets your hands in a square position at the top and encourages a full turn. If you can hold this position for a few seconds, it helps ingrain the proper feeling that you should have at the top of the swing.
Long distance hitters have a significant discrepancy between hip turn and shoulder turn. The place for a big hip turn is on the follow-through, not the backswing! One important body part that affects what the hips do is the left knee. When it collapses or bends inward, the hips are able to turn too much, making it impossible to create the necessary torque required to build clubhead speed. To improve this, simply feel the left knee staying out toward the target at the top of the backswing. This keeps some distance between the knees.
The key to hitting a golf ball a long way is minimizing your hip turn and maximizing your shoulder turn. The easiest way to accomplish this is to make sure that your left knee doesn't slide to the right on the backswing and that the right knee stays firm and flexed throughout. (Opposite knee for left-handed players.) Also, get your shoulder behind the ball at the top of the backswing. This ensures good weight shift and allows for a longer swing.
To improve distance, you must have a proper hand release in the swing. Take a short backswing and stop when your club and hands are about waist high. Look as though you are shaking hands with your thumb pointing up in the air. As you swing down into the follow through, make sure your hands are doing the same thing that they did on the backswing (thumb up). This technique ensures that you use your hands properly.
NOTE: If you have trouble hitting your clubs correctly there is a good chance that your clubs don't suit you properly.
The reason for not improving your game may well be is due to badly fitted clubs. Think about it: people come in all different shapes and sizes, but most golfers simply buy their clubs off the rack in the golf shop.
Unless you are completely 'standard' and 'average' you should consider custom fitting for your next clubs. This can be done online, and it is free, quick and easy (and doesn't hurt a bit). Visit these two sites for free online club fitting, just follow the instructions given there:
'Club Fitting Wizard' at Pinemeadow Golf
'e-fit System' at GigaGolf